Air-over-liquid hydraulic system



April 21, 1970 BECKETT ET AL 3,507,189

AIR-OVER-LIQUID HYDRAULIC SYSTEM Filed May 3, 1968 (VENT) DIRECTION AIR LIQUID [PL LIQUI INVE/V TOR S DONALD E. BECKETT WILLIAM N. BECKETT United States Patent 3,507,189 AIR-OVER-LIQUID HYDRAULIC SYSTEM Donald E. Beckett and William N. Beckett, Wilm ngton,

Ohio, assignors to Beckett-Harcum Company, Wilmington, Ohio, a corporation of Ohio Filed May 3, 1968, Ser. No. 726,310 Int. Cl. F15b 21/04, 11/08, 13/04 U.S. Cl. 914

14 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to an air-over-liquid hydraulic system for enhancing the operation of fluid motors of various types, for example double-acting and S111- gle-acting hydraulic cylinders, rotary motors, and the like.

Common practice has been to actuate fluid motors using oil under pressure, usually metered to or from the motor for controlling the speed thereof. In some applications, the motor speed must be critically regulated and controlled, and very elaborate, complex and expensive valves have been developed and used in the effort to control hydraulic motors with great precision. Better control has been sought also by the use of various types and kinds of oils, and mixtures thereof. Practices other than those mentioned above have been proposed and tried in order to achieve the precision control sought by hydraulic experts, but the problem remains unsolved.

An object of the present invention is to greatly enhance the accuracy of control for hydraulic motors.

Another object of the invention is to provide an improved hydraulic system for the accurate control of fluid motors, which involves simple and inexpensive reliable equipment that requires a minimum amount of care and servicing.

Another object is to provide a hydraulic system possessing the advantages stated, which may be used with safety and great convenience under various conditions of industrial application.

The foregoing and other objects are attained by the means described herein and illustrated upon the accompanying drawing, in which:

The drawing is a diagram of the improved hydraulic system and showing diagrammatically the various components or elements comprising the improved system.

In the drawing, a hydraulic motor is indicated at 4 comprising a cylinder in which is reciprocable a piston 6 having a piston rod 8 extending through one end wall of the cylinder. The piston rod is packed at 10 to avoid leakage of fluid from the cylinder about the rod. The cylinder is provided with major ports 12 and 14 near opposite ends thereof, through which a fluid may be fed to and exhausted from the piston chamber for driving the piston in opposite directions.

For the purposes of the present invention, hydraulic motor 4 may be one of any known type, including single-acting, double-acting, and rotary types of motors. The by way of example in explaining the invention with clarity and simplicity.

At 16 and 18 is disclosed a pair of upstanding tanks or reservoirs adapted to contain a liquid upon which air or another gaseous medium is superposed, the liquid being designated L. At the bottom of tank 16 is a port 20 which by means of a pipe 23 is placed in fluid communication with motor port 12. A port 22 of tank 18 is connected by means of a pipe 24, with the port 26 of a valve 28. A valving member 30 of valve 28 may be shifted to establish either a connection or a shut-off between port 26 and a pipe 32. Pipe 32 connects with the motor port 14.

A shunt pipe 34 may be included in the system to bypass liquid between pipes 34 and 32, Whenever valve 30 is closed. Installed in pipe 34 is a one-way metering valve 36, preferably though not necessarily of the adjustable orifice type, which permits flow of liquid only as the cylinder exhausts through port 14. Accordingly, if pressured liquid is fed into the cylinder through port 12, piston 6 will be moved to displace liquid through port 14 and valve 36 at a predetermined rate of flow. On the other hand, liquid under pressure passing from tank 18 through pipe 24 and valve 30 may pass unrestrictedly to and through motor port 14 to rapid-traverse the piston in the direction of port 12.

It should be understood that the piping and valving system shown is exemplary only, and may be altered to suit the requirements of any given motor control problem. The metering of fluid in both directions through the motor may be accomplished, if desired, by altering the system in accordance with accepted practices in the art, and various other alterations may be resorted to for adapting the system to different applications or problems encountered.

The liquid L fills the motor 4, and partially fills the tanks 16 and 18, so that displacement of liquid from one tank to the other drives the piston 6. To effect such displacement of liquid, air or other gas under pressure may be fed alternatively onto the column of liquid in either tank, through top ports 38 and 40 and pipes 42 and 44. A distribution valve 46 of suitable design is operative to direct air pressure from a source 48 to either of the tanks selectively. When air is fed to one tank for displacing liquid therefrom to operate the motor, the other tank exhauss air from the upper region thereof as will be understoo It should readily be apparent that the liquid L shifts from one tank to the other in a closed system, depending upon manipulation of control valve 46 which may be either manual or automatic. The operation of control valve 46 will be coordinated with the operation of shutoff valve 28, as is obvious. Entry of air under pressure atop the liquid in tanks 16 and 18 will be suitably bafiled, using mufllers or dispersion devices readily obtainable in the market.

A very important phase of the present invention resides in the nature of the liquid L employed in the hydraulic system. In the past, oil of one type or another was used for driving hydraulic motors, with limited success. Oils possess several undesirable characteristics in this connection, one being that it is capable of carrying air in con siderable quantity which contributes to spongy control resulting in inaccurate motor speeds or lack of uniformity piston advancement. Also, oils will foam if pressured with air, and will release air bubbles resulting in cavitation when orificed, all of which depreciates accuracy of motor operation.

In accordance with the present invention, the liquid L shall be a hydrous liquid hygroscopic in character, which will entrap little or no air and will permanently absorb and moisture or condensate developed or introduced into the fluid system. Such liquid may be said to be waterbased. One such liquid which has been found satisfactory as the hydraulic fluid L, is glycol or a material of the class of glycol, either undiluted or diluted with water. The

liquid is one which posses a low surface tension, as compared with the high surface tension of oil materials.

The use of a hydraulic liquid L of the type above mentioned assures great accuracy of motor control, and eliminates the need for complicated and expensive equipment for extracting or preventing the accumulation of air and free Water in the system. The invention contemplates the use of all hydraulic liquids which will perform as stated, to enhance flow control.

What is claimed is:

1. Apparatus for moving the impeller element of a fluid motor having a first major port and a second major port through which a liquid may be moved under pressure, said apparatus comprising: a pair of upstandin tanks each having a bottom opening in fluid communication with one of the two major ports of the fluid motor; a quantity of liquid hygroscopic of character and having the qualities of assimilating moisture andcondensate developed in the apparatus to prevent accumulation of free water therein, said liquid filling the motor and standing in stand tanks to the extent of leaving a space above the liquid therein; and means for feeding a gas under pressure alternatively into the space above the liquid in either tank, for displacing liquid from one tank to the other through said motor, thereby to move the impeller.

2. The apparatus as specified by claim 1, wherein said liquid is a water-base liquid possessing low surface tension properties.

3. The apparatus as specified by claim 1, wherein said liquid is constituted at least partly of glycol.

4. The apparatus as specified by claim 1, wherein said liquid is constituted at least partly of a material of the class of glycol.

5. The apparatus as specified by claim 1, wherein said liquid is a hydrous liquid.

6. The apparatus as specified by claim 1, wherein means is interposed between the bottom opening of one tank and a major port of the motor, for regulating the.

flow of liquid through the ports of the motor.

7. The apparatus as specified by claim 1, wherein is included a fluid pipe interconnecting the bottom opening of one tank with said one major port of the fluid motor, said pipe having interposed therein a shut-off valve for alternatively permitting or closing off flow through said pipe; and a shunt pipe intermediate said bottom opening of said one tank and said major port, said shunt pipe ineluding a metering valve operative to control the rate of liquid flow through the shunt pipe and the motor ports when the shut-off valve is in closed position.

8. The apparatus as specified by claim 7, wherein said metering valve is adjustable as to the flow of liquid therethrough.

9. The apparatus as specified by claim 7, wherein the fluid motor is a hydraulic cylinder having a chamber with.

a piston therein, and a piston rod projecting from one end of the cylinder through a portion of said chamber, said.

12. The apparatus as specified by claim 7, wherein said liquid is constituted at least partly of a material of the class of glycol.

13. Apparatus as specified by claim 1, wherein is included an unimpeded first fluid conduit interconnecting the bottom opening of one tank with said first major port of the fluid motor for free flow of liquid therethrough; a second fluid conduit interconnecting the bottom opening of the other tank with said second major port, said second fluid conduit being divided into two parallel conduit portions intermediate the other tank bottom openin and said second major port, one of said parallel conduit portions having a one-way metering valve therein for metering flow from said second major port to said tank bottom opening and precluding flow therethrough in the reverse direction,

the other of said parallel conduit portions having a shutoff valve therein for selectively preventing and permitting flow therethrough.

14. Apparatus for moving the impeller element of a fluid motor having a first major port and a second major port through which a liquid may be moved under pressure, said apparatus comprising: a pair of upstanding tanks each having a bottom opening in fluid communication with one of the two major ports of a fluid motor; a quantity of liquid filling the motor and standing in said tanks to the extent of leaving a space above the liquid therein; means for feeding a gas under pressure alternatively into the space above the liquid in either tank, for displacing liquid from one tank to the other through said motor, a fluid pipe interconnecting the bottom opening of one tank with said one major port of the fluid motor,

said pipe having interposed therein a shut-01f valve for.

alternatively permitting or closing off flow through said pipe; and a shunt pipe intermediate said bottom opening of said one tank and said major port, said shunt pipe ineluding a one-way adjustable metering valve operative to control the rate of liquid flow from said one major part through the shunt pipe, said fluid motor being a hydraulic cylinder having a chamber with a piston therein, and a piston rod projecting from one end of the cylinder through a portion of said chamber, said one major port of the fluid motor aforesaid being influid communication with that portion of the cylinder chamber which contains the piston rod, and said liquid being constituted at least partly of a material of the class of glycol.

References Cited UNITED STATES PATENTS OTHER REFERENCES Hydraulic Handbook, 2nd edition, published by Trade and Technical Press, Limited, Marden, Surrey, England,

1960; pp. 211 to 221; T1 840, H 97, 1960 C3. PAUL E. MASLOUSKY, Primary Examiner US. (:1. X.R. 91-466; 92-142 

